At PFF you wait in very long lines and you never know which princess you are going to get at PFF. I believe they only have 1 or 2 out at a time and they rotate regularly.
We went to the Ariel lunch last October. You meet and get your photo taken with Ariel at the door. We had Cinderella, Snow White, Fairy Godmother and Belle. They each came to our table to converse, sign autographs and take pictures.
I figure if you're going to use up an hour of your day, you might as well be seated in nice cool place eating, while getting a chance to interact with the characters. Its like killing 2 birds with 1 stone, so to speak.